package reflection;

import java.util.*;
import java.lang.reflect.*;

/**
 * This program uses reflection to print all features of a class
 * @version 1.1 2020-0-8
 * @author Shan Zhang
 */

public class ReflectionTest {

    public static void main(String[] args) {
        // read class name from command line args or user input
        String name;
        if (args.length > 0) name = args[0];
        else {
            Scanner in = new Scanner(System.in);
            System.out.println("Enter class name (e.g java.util.Date): ");
            name = in.next();
        }

        try {
            // print class name and superclass name (if !=Object)
            Class cl = Class.forName(name);
            Class supercl = cl.getSuperclass();
            String modifiers = Modifier.toString(cl.getModifiers());  // 它将返回一个整型数值， 用不同的位开关描述 public 和 static 这样的修饰符使用状况
            if (modifiers.length() > 0) 
                System.out.print(modifiers + " ");
                System.out.print("class" + name);
    
            if (supercl != null && supercl != Object.class) 
                System.out.print(" extends" + supercl.getName());
                System.out.print("\n{\n");
                printConstructors(cl);
                System.out.println();
                printMethods(cl);
                System.out.println();
                printFields(cl);
                System.out.println("}");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
        System.exit(0);
    }

    /**
     * Prints all constructors of a class
     * @param cl a class
     */
    public static void printConstructors(Class cl) {

        Constructor[] constructors = cl.getDeclaredConstructors();

        for (Constructor c: constructors) {
            String name = c.getName();
            System.out.print("");
            String modifiers = Modifier.toString(c.getModifiers());
            if (modifiers.length() > 0)
                System.out.print(modifiers + " ");
                System.out.print(name + "(");
                // print parameter types
                Class[] paramTypes = c.getParameterTypes();
                for (int j = 0; j < paramTypes.length; j++) {
                    if (j>0) 
                        System.out.print(", ");
                        System.out.print(paramTypes[j].getName());
                }
                System.out.println(");");
        }
    }
    /**
     * Prints all methods of a class
     * @param cl a class
     */
    public static void printMethods(Class cl) {
        Method[] methods = cl.getDeclaredMethods();

        for (Method m:methods) {
            Class retType = m.getReturnType();
            String name = m.getName();

            System.out.print("    ");
            // print modifiers,return type and method name
            String modifiers = Modifier.toString(m.getModifiers());
            if (modifiers.length() > 0)
                System.out.print(modifiers + " ");
                System.out.print(retType.getName() + " " + name + "(");
                // print parameter types
                Class[] paramTypes = m.getParameterTypes();
                for (int j=0;j < paramTypes.length;j++) {
                    if (j>0)
                        System.out.print(",");
                        System.out.print(paramTypes[j].getName());
                }
                System.out.println(");");
        }
    }
    /**
     * prints all fields of a class
     * @param cl a class
     */
    public static void printFields(Class cl) {
        Field[] fields = cl.getDeclaredFields();
        
        for (Field f : fields) {
            Class type = f.getType();
            String name = f.getName();
            System.out.print("  ");
            String modifiers = Modifier.toString(f.getModifiers());
            if (modifiers.length() >0 )
                System.out.print(modifiers + "  ");
                System.out.println(type.getName() + " " + name + ";");
        }
    }
}   